Fig. 3.

Schematic illustration of the peak sharpening process in the separation column and general requirement of sharp peak formation. Upper diagram shows a portion of the separation column that contains organic stationary phase in the upper half and aqueous mobile phase in the lower half. The acid present in the sample solution forms a sharp trailing border around which the solute molecules circulate by repeated protonation (on the right side) and deprotonation (on the left side) to form a sharp peak as described in the text. The lower diagram shows the requirement for sharp peak formation. Peak 1 is obtained when both K_a and K_b are smaller than K_r, while peak 3 is obtained when both K_a and K_b are greater than K_r. Sharp peak 2 is only formed when K_r falls between K_a and K_b, as indicated in the figure.